But little did anyone watching know that while rehearsing the number a week prior, Settle had lost half of her body’s motor functions due to a mini-stroke — one that would lead doctors to diagnose her with a rare cerebrovascular disorder known as Moyamoya disease.

Now, six months after undergoing a 10-hour double-bypass brain surgery to correct the problem, Settle is speaking out for the first time about her health crisis in this week’s PEOPLE, admitting it changed her for the better.

“It’s shifted me in ways I’m still understanding,” she marvels. “The way that I look at the world is so completely different. I’m more at peace than I’ve ever been; I can find the joy in things I never could. This truly gave me another lease on life.”

Trouble first started for Settle in the weeks leading up to the Oscars. She had been on a non-stop worldwide promotional tour for The Greatest Showman and its chart-topping soundtrack, a process that left her immune system compromised and her patience, understandably thin. “I was completely rundown,” she says. “I had gotten food poisoning in Tokyo, I was fighting a cold. I barely had anything left to give.”

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Stepping into a rehearsal space in Burbank, Calif., on Saturday, Feb. 24, Settle’s stress levels were high — so much so that she ended up having a nervous breakdown on set. Collapsing into tears, she suddenly felt a shooting pain in her skull and noticed the right side of her body go completely numb. “It was like someone cracked an egg on the top of my head and then drew a line on my body, turning one half off,” she recalls. “My body started drooping immediately. I tried to put my hands up to my face, but I could only move my left arm. I couldn’t talk because part of my tongue was immobile. I tried to stand, but there was nothing.”

“I was panicked,” she continues. “I let out this wail because I was so scared and the room went silent. All I could figure out how to say was ‘Help.’ “

Settle had suffered from a transient ischemic attack (TIA), a “mini-stroke” that produces similar symptoms of a larger stroke, often as a warning of impending trouble.

Her facilities were back within 20 minutes of the TIA’s dissipation, but a series of brain scans over the next few days in the hospital showed that her problem was much worse. Half of Settle’s brain was actually blocked from blood flow and oxygen for years due to collated carotid arteries (the major blood vessels in the neck that supply blood to the brain, neck, and face). To compensate, her brain had created tiny blood vessels at the base to supply it with blood (their shape earning the name “Moyamoya disease,” Japanese for “puff of smoke”). Those weak vessels were now completely dried out. Subsequently, they snapped.

“It could have happened at any time,” Settle explains, noting that the condition is prevalent in a lot of women, specifically Asian Pacific Islanders. “It just so happened to happen a week before the biggest performance of my life.”

With days to go before taking the stage, Settle — a Tony nominee with roles in Waitress and Les Misérables — decided to delay surgery (“I’m used to working in the theater and the show must go on,” she jokes).

By Wednesday she was home and back in rehearsals, no one the wiser. She was put on anti-seizure medications, children’s aspirin, and encouraged to stay hydrated to maintain blood flow.

Four days later, Settle was in front of millions of viewers — singing what she calls, “the song that almost killed me.”

Surgery finally came on April 27, after a 5-week pre-op process. The operation provided alternative blood flow to the right side of her brain for the first time ever.

With it came a sea of new challenges, one that music producer Greg Wells helped her overcome by moving her into his Los Angeles home for her first month of recovery. “I have a new brain and that’s meant starting over,” she says, adding that her family and friends were with her during a six-day stay in the ICU. “I needed a blood transfusion to help move, and then I spent the entire first month doing a lot of cognitive and physical therapy to relearn how to walk, talk, write, and live life again. I’ve been growing my memory, too. It’s all a process and I’m still working on it daily.”

Moyamoya disease is not curable. Though surgery has provided Settle with significant stroke-risk reduction, she will be on medication for the rest of her life.